This invention relates to inertial instruments, such as gyroscopes and accelerometers, and more specifically to bias error correction in such instruments.
The performance of inertial instruments is degraded by bias, a measure of the deviation of a measurement made by a non-ideal inertial instrument from a measurement made by a perfect or ideal instrument. For example, the bias of a gyroscope is determined by the difference between the gyroscope's reading at a zero angular rate and zero which would be measured by a perfect gyroscope. Bias drift is a rate of change of the bias resulting from changes such as environmental conditions over time.
One method of compensation for bias and/or bias drift in an inertial instrument is to periodically make bias correction adjustments of the inertial instrument based on information obtained from another source of known accuracy. For example, global positioning satellite (GPS) signals processed by a GPS receiver co-located with the inertial instrument can be used to determine a series of locations over known time intervals. This GPS information can be utilized to periodically recalibrate a bias error correction signal of the inertial instrument to make the output coincide with the GPS data. However, depending upon the operational environment, the reception of GPS signals is not always possible, and hence correction of the inertial instrument's output based on GPS data cannot always be relied upon. Therefore, a need exists to minimize bias and bias drift in an inertial instrument without requiring a separate source of accurate positional information such as derived from GPS information or the like.